package j20251103;

public class Solution3 {
    boolean[][] vis;
    int m,n,ret;
    int[] dx={0,0,1,-1};
    int[] dy={1,-1,0,0};
    public int numIslands(char[][] grid) {
        m=grid.length;
        n=grid[0].length;
        vis=new boolean[m][n];
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                if(!vis[i][j]&&grid[i][j]=='1'){
                    dfs(grid,i,j);
                    ret++;
                }
            }
        }
        return ret;
    }
    public void dfs(char[][] grid,int i,int j){
        for(int k=0;k<4;k++){
            int x=i+dx[k],y=j+dy[k];
            if(x>=0&&x<m&&y>=0&&y<n&&!vis[x][y]&&grid[x][y]=='1'){
                vis[x][y]=true;
                dfs(grid,x,y);
                grid[x][y]='0';
                vis[x][y]=false;
            }
        }
    }
}
